Technical Abstract:
Mass-rearing is underutilized in biological weed control, despite the wealth of biological information available for insects that have been released and the utility of inoculative releases using large numbers of insects to maximize establishment. Mass-rearing is particularly uncommon for biological control insects that cause abnormal growths or galls in weed tissues. Galling insects are highly host-specific and have high impact potential. We developed a mass-rearing system for the arundo wasp Tetramesa romana (Hymenoptera: Eurytomidae) which galls shoot tips on arundo, also known as giant reed or carrizo cane (Arundo donax), a non-native, invasive giant perennial grass of riparian ecosystems that is causing major environmental and economic damage in the Lower Rio Grande Basin and other arid watersheds in North America. The protocol optimized conditions for production of vigorous arundo shoots, wasp oviposition behavior and survival on shoot tips, gall development, and collection of progeny, amplifying the wasp population every 30-40 days for most of the year. An artificial diet induced larval feeding but did not support wasp development. Wasps mass-reared on plants have established populations on arundo along 500 km of the Rio Grande. The mass-rearing procedure and underlying concepts can be applied to other weed biological control systems.